In 1909 the Danish dentist Viggo Andresen removed his daughter’s fixed appliance and replaced it with a Hawley retainer, which he had modified with a lower arch wire designed to move the mandible. The appliance worked in correcting Andresen’s daughter’s class II malocclusion, so Andresen began to explore ways to develop his appliance further. The Andresen appliance was a passive appliance which was only worn at nighttime. It sat in the mouth and was held in place by the work of the muscles around it. The activator was designed to move the mandible forward for the correction of Class II malocclusions and to open the bite. It could also direct erupting back teeth meaning it could change dental relationships in all three planes of space.

Andresen later worked with the Austrian pathologist Karl Häupl to develop the Norweigan system of functional jaw orthopaedics. Andresen’s appliance would go on to be modified by others, producing new types of appliance.